What is the construction design of an underground cable characterized as?

The construction design of an underground cable is characterized by having a non-conductive sheath. This sheath plays a crucial role in protecting the conductor from environmental factors such as moisture, chemicals, and mechanical damage. The non-conductive material ensures that the electricity travels through the conductor without leaking, maintaining safety and efficiency.

In the context of underground cables, the design typically includes several layers, which might involve conductive materials for the core, insulation layers, and the outer non-conductive sheath. This outer layer is essential for providing a barrier that prevents short circuits and electrical faults that could occur if moisture or impurities come into contact with the conductive materials.

The other options do not accurately describe the key aspect of underground cable construction. For example, a flexible conduit may be used for some installations but does not specifically characterize the overall design of underground cables. A tubular capacitor is unrelated to cable structures and instead pertains to electrical components that manage power levels. Rigid aluminum encasement, while it might be used in some situations, does not describe the typical need for a non-conductive outer layer that protects the cable and its function.